Terraces are earthen structures that intercept runoff on moderate to steep slopes. They transform long slopes into a series of shorter slopes. Terraces reduce the rate of runoff and allow soil particles to settle out. The resulting cleaner water is then carried off the field in a non-erosive manner. Terraces are used to reduce sheet and rill erosion and prevent gully development.
They are most effective when used in combination with other practices such as conservation tillage, crop rotations, and field borders. Terracing reduces sediment pollution of lakes and streams. Grassed front-slopes and back-slopes of some terraces provide cover for wildlife.
Grassed backslope terraces have a farmable frontslope with a 2:1 backslope (2 feet horizontal to every 1 foot of vertical drop).
Narrow base terraces have 2:1 slopes on both the frontslope and backslope.
Broadbase terraces are flatter looking terraces that are farmed on both slopes. They should not be built on land slopes greater than 6 percent. Farmable slopes should not be steeper than 5:1.